Need a sanity check... 
If you use a Button to change the 'Visible' property of a DataCard in an EditForm so that you can hide or show a field, it works in the browser, but 'breaks' in the latest iPhone App ver 3.18063.36. Was working a few versions ago. Can't say what version.
This is the standard workaround that is used to create the "illusion" of Tabs on a screen.
To test I created an App from Scratch using a SharePoint List and then I did the following:
- In the EditForm Screen, Selected a DataCard representing a Field (Title) and changed the Visible property to - FormVar="General"
- Created a Button called "General" and set the OnSelect property to - Set(FormVar,"General")
- Created a second Button called "Status" and set the OnSelect property to - Set(FormVar,"Status")
- Set the Screen OnVisible property to - Set(FormVar,"General")
When you first come into the screen, the "Title" field displays correctly and allows you to change the value.

When you press the Button "Status", the "Title" field disappears as it should.
When you press the Button "General", the "Title" field appears again but you can't see the data portion and you can't edit it.

Is anyone experiancing this?